The invention relates to a method for stopping conveying equipment for persons and to a safety circuit for monitoring the stopping.
The use of the term xe2x80x9cconveying equipment for personsxe2x80x9d herein is to be understood to encompass not only escalators, but also moving walkways.
A method for braking rolling stairs or rolling walkways have become known from DE 198 03 899 C2, in which, on response of a safety element motor, a drive frequency converter is controlled and a braking ramp is activated, by way of which the speed of the step belt or plate belt is brought to a zero value with substantially uniform delay. The holding brake is activated at the instant of standstill of the rolling stairs or the rolling walkway. The frequency converter ensures that the rolling stairs or rolling walkway is braked according to the set braking ramp, wherein monitoring of the braking system takes place in the region of the control. The monitoring of faults in the region of the frequency converter and/or the control is performed by additional safety elements.
In such methodology additional safety elements are not monitored. In the case of the faulty function of an additional safety element the function of the frequency converter and/or the control thus cannot be checked, which can lead to an uncontrollable braking process.
The present invention has an object of proposing a method and a safety circuit which do not have the aforesaid disadvantages and ensures a reliable braking system free of disturbance.
In accordance with the foregoing and other objects and purposes, the present invention is a method and apparatus for stopping conveying equipment for persons of the type in which a braking process is performed by a frequency converter coupled to a drive motor by which the conveying equipment for persons is brought to a stop or standstill, wherein the braking process is monitored by a drive safety circuit having at least first and second channels.
The presence of at least two channels ensures increased safety. Certain functions of the braking system can be monitored at least twice and independently of one another. The operational safety of the braking system is therefore increased.
Advantageously, the first channel may be provided with a first processor control and the second channel with a second processor control. This has the advantage that the system can be parameterised in simple manner and mutual checking can be carried out by way of a bus system.
Advantageously, the first channel and the second channel monitor one another. This provides a redundant system. If one channel does not function in orderly manner, this is recognized by the other channel. Appropriate safety measures can then be initiated.
All explained features are usable not only in the respectively stated combination, but also in other combinations or by themselves without departing from the scope of the invention.